Manipulators of the type commonly used in robotics applications and for supporting a workpiece or tool commonly include a plurality of articulated links joined together serially, starting with a fixed or mobile base, in end-to-end relation. A plurality of actuators are provided, one at each pivotal connection of the links, to effect movement of the links with respect to one another.
In order to produce a manipulator wherein the load or tool supported by the manipulator will be moveable with six degrees of freedom, commonly the manipulator is comprised of a plurality of links joined together in end-to-end relation, and a number of actuators are provided to produce movement of the links with respect to one another, each actuator in turn being supported by one of the links at the respective joint between links.
One of the characteristics of this arrangement is that the actuators supporting serially connected links must be capable of supporting the mass of all of the other actuators as well as the mass of the links, and the inertia experienced by one actuator will include the inertia of the links and the inertia of the actuators supported by that actuator as well as the inertia of the tool or load supported by the articulated linkage.
When such articulated linkages are used in robotics to support a tool, the position of the tool must be continually sensed. Another characteristic of the prior art manipulator linkages is that calculation of the position of a link at the end of the articulated linkage requires a sequential calculation of the relative position of each of the supporting links and actuators. A change in the position of one of the supported actuators and associated link will result in a change of the position of all of the links and actuators supported by that link. Accordingly, when the positions are calculated, the calculations must be made in sequence, first calculating the position of a base link and then serially the links supported by that first link. Because these calculations must be done in sequence, the calculation process can limit the speed of movement or operation of the manipulator and the tools supported by the manipulator.